Enhancing the performance of wireless networks with packet level forward error correction

Wireless networks experience high packet loss rates due to low quality links. To create reliable connectivity between the source and the destination so that all packets are guaranteed to be delivered, Automatic Repeat Request (ARQ) is a commonly deployed mechanism. However, the ARQ creates a jitter in the packet arrival times that can cause prohibitive delays in real-time communications. To address this problem, this thesis investigates a modification to the ARQ scheme by introducing hybrid ARQ and packet level Forward Error Correction (FEC). While an ARQ scheme alone is sufficient to guarantee successful data transmission, this thesis shows that a hybrid packet level FEC/ARQ system offers enhanced throughput performance with reduced delay effects.; Two implementations for packet loss recovery using packet level FEC to aid ARQ operation are pursued in this thesis: (i) end-to-end, and (ii) hop-by-hop. End-toend packet loss recovery uses packet level FEC only at the destination node of a network, and is the focus of existing work in the literature. Hop-by-hop packet loss recovery is facilitated throughout the network with the use of regenerating nodes, where forward error recovery is performed at intermediate nodes and the destination. The regenerating nodes reduce the packet loss rate (PLR) between the source and the intermediate nodes by minimizing the accumulated number of lost packets at the destination. The throughput and delay performance tradeoffs for the hybrid FEC/ARQ system are documented in this thesis. The regenerating node concept was originally envisioned to only use packet level FEC, but this work considers the combination of packet level FEC with different ARQ mechanisms to examine the effect of this combination on throughput and packet delivery delay. Specifically, it is found that when a hybrid packet erasure FEC/ARQ mechanism is incorporated into regenerating node functionality, an improved throughput results in comparison to using FEC alone as implemented in the past.; To take advantage of having multiple links to the destination, two dimensional (2-D) Reed-Solomon product codes are introduced for packet level FEC in conjunction with regenerating nodes. It is shown that when these codes are used in a hybrid FEC/ARQ packet erasure recovery scheme, there are improvements in throughput over a standard one dimensional (1-D) coding scheme. This improvement in throughput comes at the cost of an increase in decoding delay when considering an end-to-end 2-D packet erasure mechanism, and when considering hop-by-hop 2-D decoding functionality, the decoding delay is shown to be prohibitive. It is found in this work that a combination of hop-by-hop 1-D packet erasure recovery functionality combined with an end-to-end 2-D packet erasure recovery mechanism, provides a reasonable trade-off between decoding delay and throughput.; The main contribution of this work is in showing that a combination of hybrid packet erasure FEC/ARQ based on positive acknowledgements with 1-D R-S regenerating node functionality, and 2-D R-S end-to-end packet erasure recovery, offers the best compromise for throughput performance and delay in a multi-hop wireless network.